During the making of “Zero Dark Thirty,” Jessica Chastain was given a crash course in the less-is-more approach to screen acting.

Since making her film debut a little over a year ago, the actress has wowed critics and audiences alike with an array of characters ranging from an effervescent housewife in “The Help” to a courageous Israeli spy in “The Debt” to a weary former prostitute in “Lawless.”

But “Zero Dark Thirty,” the saga of a C.I.A. agent’s 10-year mission to capture Osama bin Laden, required an almost minimalistic performance from Chastain.

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“I’m playing a character who’s trained to be unemotional and analytically precise,” says the actress. “As an actor, you spend your whole life trying to be emotional and keeping yourself emotionally open. So, to find the humanity within that, in that arc, was a great (challenge) for me.”

If early reviews are any indication, Chastain met the challenge like an old pro.

Written by Mark Boal and directed by Kathryn Bigelow — the same team behind the Oscar-winning “Hurt Locker” — “Zero Dark Thirty” begins on 9/11 and ends with the shooting of Bin Laden at his compound in Abbottabad, Pakistan.

In between, the film encompasses scores of events spanning nearly a decade in multiple countries around the globe. Since Boal and Bigelow’s intention was to “capture the on-the-ground reality of this mission as truthfully and viscerally as possible,” they opted to document the moral lines — including torture — that were crossed.

The whole saga pivots on a little-known participant in the intel hunt: Maya (Chastain), a young CIA officer who was central in tracking down Bin Laden’s whereabouts. Maya is based on an actual CIA agent who remains an undercover agent to this day.

“When I was reading the script, every page that I turned was a shock to me, especially about Maya and the role she took in (the capture of Bin Laden),” says Chastain.

“Then I got upset that it was such a shock to me. Why would I assume a woman wouldn’t be involved in this kind of research? The wonderful thing about working on this film is, historically, in movies, lead characters are played by women who are defined by men, whether as a love interest or as a victim of a man. Maya’s not like that.”

Buoyed by outstanding reviews, “Zero Dark Thirty” instantly became the favorite to win this year’s Best Picture Oscar. The New York Times called it a “wrenchingly sad, soul-shaking story about revenge and its moral costs” while New York magazine raved that it’s a “a phenomenal piece of action filmmaking.”

But some commentators have taken issue with the movie’s refusal to condemn techniques like waterboarding and the forcing of detainees into stress positions.

“Zero Dark Thirty” (the title is military jargon for the dark of night, as well as the moment — 12:30 a.m. — when the Navy SEALs first stepped foot on the compound) has proven so controversial, in fact, that a trio of senators (Dianne Feinstein, John McCain and Carl Levin) wrote a letter to Sony Pictures calling the film “grossly inaccurate and misleading in its suggestion that torture resulted in information that led to the location” of Bin Laden.

In response, Sony released a statement from Bigelow and Boal in which the filmmakers’ argue that they depicted “a variety of controversial practices and intelligence methods that were used in the name of finding Bin Laden. The film shows that no single method was necessarily responsible for solving the manhunt, nor can any single scene taken in isolation fairly capture the totality of efforts the film dramatizes.”

In some sense, Maya’s development, from innocence to determination, reflects the evolution of America as it attempts to deal with what the filmmakers call “the ruthless calculus of terrorism.”

According to Chastain, the interrogation scenes, which comprise a very small portion of the film, were among the hardest to shoot.

“Those scenes, they were tough, to be honest,” she says. “We filmed that section of the movie in a Jordanian prison, so we weren’t on a sound stage in Los Angeles…. That was a tough week.

“But it’s like Kathryn has said, `it’s a part of the history of the characters.’ So instead of looking at it and making my own judgments on what I personally believe is right and wrong, I try to look at it in terms of the character. “

While “Zero Dark Thirty” celebrates the efforts of hundreds of hard-working C.I.A. agents to get the job done, politics are kept out of the equation.

“It’s not a propaganda movie,” says Chastain. “It’s not, ‘Go America.’ It’s (a movie told) through the eyes of this woman who became such a servant to her work that she lost herself along the way.

“(After Bin Laden is killed), there’s the question, ‘Where does she go now?’ But then also you have to ask, ‘where do we go as a country? Where do we go as a society?’ I find that ending the film on that question is far more interesting than providing an answer.”

Filming primarily in Jordan and India allowed the actors to feel as if they were, in Chastain’s words, “immersed in the story.”

Chastain was particularly determined to take her job home with her.

“I had the props person print out all the pictures of the terrorists that Maya looks at and I actually hung them in my hotel room. So, even when I would come home from set, it was always around me.”

Born and raised in Northern California, Chastain can’t remember a time when she didn’t want to be an actor. She studied at the prestigious Juilliard School in New York before scoring in a handful of Broadway and off-Broadway productions, including “Rodney’s Wife” opposite David Strathairn. She also starred alongside Al Pacino in an L.A. production of “Salome.”

She made her film debut in 2010’s “Jolene,” which was barely released in theaters. Her 2011 movies — “The Help,” “The Debt,” “Texas Killing Fields,” “Coriolanus” and “Tree of Life” — scored much better.

With her 2013 films in the can, including the horror film “Mama” and “Eleanor Rigby” with James McAvoy, Chastain is now starring in a Broadway revival of “The Heiress,” the 1947 adaptation of the Henry James’ 1880 novel “Washington Square.” The production closes in February.

“I’m a crazy person,” she said. “I think my first film came only out a-year-and-a-half ago. I’m really lucky to do what I do, but I’ll tell you right now, it’s a very strange thing to be talking about Maya and then think, ‘OK, at 6:30 p.m., I’m going to start putting my hair in pin curls and go on stage as Catherine Sloper in ‘The Heiress.’”

“But it’s a great gift. The character of Maya is very different from me because I am a very emotional girl and very sensitive. I like to have a good time. I’m very smiley. Even though she’s very different there is something that is similar and that’s (that we’re both) in love with our work.

“I can understand that passion, that sense of servitude, some might say ... I’m nowhere near the amazing woman that Maya is. But I do understand her. A love of what I do is what gets me on stage every night.”